In the field of peripheral intervention, devices known as infusion catheters are commonly used to deliver a therapeutic treatment fluid to an intraluminal treatment site within a body lumen, such as a vein or artery. One general class of infusion catheters utilizes a longitudinally extending passage which fluidly connects a supply of treatment fluid located outside of the patient with the treatment site by way of ports formed in a body of the infusion catheter. A typical infusion procedure involves leaving an infusion catheter within a patient for a period of time while treatment fluid flows from the fluid supply into the infusion catheter, and thenceforth into the body lumen. One common application of infusion catheters is the treatment of clots or other undesired tissues which have formed within a vein or artery. Treatment fluids commonly referred to as thrombolytic agents are often used to dissolve clot material.
While various infusion techniques have been used for many years, they are not without shortcomings. Basic assumptions about the operation and behavior of infusion catheters while resident in a vein or artery, for example, may not always be true. For instance, it is often assumed that all portions of an infusion length of an infusion catheter will predictably, reliably and uniformly infuse fluid into the treatment site throughout the entire course of an infusion procedure. In some instances, however, portions of an infusion catheter and, notably, more distal portions, may actually be supplying little or no treatment fluid. This phenomenon is believed to result at least in part from the loss in pressure of the treatment fluid as it flows in a proximal to distal direction through the infusion catheter. When the treatment fluid arrives at a distal region of an infusion catheter, there may be insufficient pressure for the treatment fluid to overcome a fluid pressure such as a pressure of blood within the body lumen to be treated. As a result, infusion procedures may be ineffective, require undue lengths of time, or have other shortcomings such as the oversupply of treatment fluid to compensate for non-uniformity in distribution.
Clinicians have experimented with various strategies for improving uniformity of treatment fluid distribution from an infusion catheter. One known strategy is to provide a non-uniform distribution of infusion ports in the catheter body, with the infusion ports being relatively few in number in a proximal portion of an infusion catheter and relatively great in number in a distal portion. This strategy is believed to at least somewhat overcome the problems associated with fluid pressure loss noted above. Other strategies include configuring an infusion catheter such that all or part of the infusion length of the catheter functions as a valve. This technique allows fluid pressure to build within the infusion catheter, and then actuate the valve to provide a burst of treatment fluid into the body lumen which is believed to be relatively uniform. While these and other techniques have met with some success, there remains room for improvement.